A question about brakes

[darwins]

So far as I can see there may be six 'air' brake types in use in UK today.

1. Single Pipe Air Brake

2. Twin Pipe Air Brake
- normal application and release from front of train

3. "HST" Twin Pipe Air Brake
- Wescode / E70 system application from both ends of train at the same time, release from front of train

4. Indirect EP Brake
- EP brake applied without reduction in ABP pressure ( as historically used for 4-EPB, class 312 etc )

5. EP Assisted Air Brake
- EP brake applied together with reduction in ABP pressure ( for example using PBL 90 )

6. Direct EP Brake
- EP brake only with ABP replaced by electrical continuity circuit ( eg 3-step or pulse modulated )


Which of these types of brake is used on which types of train?
I hope the list below is more or less correct, but corrections and additions would be welcomed.

1. Single Pipe Air Brake
- the easy one - Freight trains (are there any exceptions?)

2. Twin Pipe Air Brake
- "loco" hauled passenger trains ( class 37 + Mk2 DVT, heritage excursion trains Mk1, Mk2, Mk3 stock )
- Mk 4 carriages and DVTs?

3. "HST" Twin Pipe Air Brake
- HST, Class 90 or Class 91 with Mk 3 DVT or Mk 4 DVT

4. Indirect EP Brake
- class 442, 455, 456

5. EP Assisted Air Brake
- is this used in practice? Eurostar trains? Pendolinos? and Voyagers/Meridians? 80x??

6. Direct EP Brake
3 step brake - classes 150 to 168, classes 313 to 333, Networkers, Electrostars,
Pulse modulated brake - classes 170 to 185, class395, Junipers, Desiros, Aventras,


Where do Pendolinos and Voyagers/Meridians come on this list? They appear to have a 7-step EP brake ( DW3 / E70 ) and it has been posted elsewhere that they have a standard twin pipe air system. This suggests to me that they must be either #4 or #5 above. So I have guessed that they will be in #5 in order to meet UIC standards. Are the IEP units also in this category?

 

[100andthirty]

All of todays multiple unit trains don't have a brake pipe at all. The compressed air line down the train merely feeds a compressed air supply to air reservoirs on each coach. Brake control is carried out entirely electrically, and sorts out when dynamic braking and when friction braking is used and when the former needs to be supplanted by the latter. The brake control doesn't have "steps" as such.

 

[GC class B1]

So far as I can see there may be six 'air' brake types in use in UK today.

1. Single Pipe Air Brake

2. Twin Pipe Air Brake
- normal application and release from front of train

3. "HST" Twin Pipe Air Brake
- Wescode / E70 system application from both ends of train at the same time, release from front of train

4. Indirect EP Brake
- EP brake applied without reduction in ABP pressure ( as historically used for 4-EPB, class 312 etc )

5. EP Assisted Air Brake
- EP brake applied together with reduction in ABP pressure ( for example using PBL 90 )

6. Direct EP Brake
- EP brake only with ABP replaced by electrical continuity circuit ( eg 3-step or pulse modulated )


Which of these types of brake is used on which types of train?
I hope the list below is more or less correct, but corrections and additions would be welcomed.

1. Single Pipe Air Brake
- the easy one - Freight trains (are there any exceptions?)

2. Twin Pipe Air Brake
- "loco" hauled passenger trains ( class 37 + Mk2 DVT, heritage excursion trains Mk1, Mk2, Mk3 stock )
- Mk 4 carriages and DVTs?

3. "HST" Twin Pipe Air Brake
- HST, Class 90 or Class 91 with Mk 3 DVT or Mk 4 DVT

4. Indirect EP Brake
- class 442, 455, 456

5. EP Assisted Air Brake
- is this used in practice? Eurostar trains? Pendolinos? and Voyagers/Meridians? 80x??

6. Direct EP Brake
3 step brake - classes 150 to 168, classes 313 to 333, Networkers, Electrostars,
Pulse modulated brake - classes 170 to 185, class395, Junipers, Desiros, Aventras,


Where do Pendolinos and Voyagers/Meridians come on this list? They appear to have a 7-step EP brake ( DW3 / E70 ) and it has been posted elsewhere that they have a standard twin pipe air system. This suggests to me that they must be either #4 or #5 above. So I have guessed that they will be in #5 in order to meet UIC standards. Are the IEP units also in this category?

I would suggest that your items 1) and 2) are the same as they are classified as the UIC brake and all two pipe systems can be operated as single pipe.

I understand that item 3 is still a UIC brake and only the cab controller differs, the brake systems operates in essentially the same way as a locomotive hauled two pipe air brake but applies the brake from both ends of the train to speed up application but can only be released from the active cab.

I don’t think item 5 exists In this country. The NIR class 80 DMUs which are now all withdrawn had a straight air brake with e.p. assist to speed up the application rate.
Old SR emus had an energise to apply e.p. Brake that was not fail safe. These had a brake pipe that was always charged to 70 psi and in even of train division or failure of the e.p. Brake venting this pipe initi and Emergency brake application. These systems are now only on heritage units.

An older system was fitted to SR EMUs built before the e.p. Braked SR emus. These had a pneumatic brake with a triple valve and not a distributor (I.e. not a UIC brake).

Voyagers and meridians have an energise to release ep brake ( your item 6). This is fail safe. As on all other vehicles except single piped freight wagons there is a Main Reservoir (yellow) pipe along the train that supplies air to the Brake Supply Reservoir to feed compressed air to the brake actuators. The Main Reservoir Pipes also supply compressed air to other systems such as the body side door air seals.
The brake pipe on these vices is normally at atmosphere as it is only used for recovery. In the event that the unit requires to be hauled by a locomotive the brake pipe is charged to 5 bar and the brake system effectively becomes a two pipe air brake with the brake being released by the charged brake pipe without any ep electrical signal being needed.

All of todays multiple unit trains don't have a brake pipe at all. The compressed air line down the train merely feeds a compressed air supply to air reservoirs on each coach. Brake control is carried out entirely electrically, and sorts out when dynamic braking and when friction braking is used and when the former needs to be supplanted by the latter. The brake control doesn't have "steps" as such.

DMUs have a 3 step energise to release ep brake.

I think class 800 also have an energise to release e.p. Brake controlled by a PWM signal from the brake controller. There are no brake steps on class 800 as the brake is continuously variable.

 

[darwins]

I would suggest that your items 1) and 2) are the same as they are classified as the UIC brake and all two pipe systems can be operated as single pipe.

Thanks very much for a comprehensive answer.

All of the systems, except (6) have an air brake pipe and therefore can be operated as single pipe. Systems (2), (3), (4) and (5) also have a main reservoir pipe so could all be operated as twin pipe.

System (6) as described has a continuity circuit in place of the air brake pipe, so can not be operated as air single pipe. So it is very interesting to read your response that Voyager and Meridian trains have this system for normal operation, but also include an air brake pipe for emergency operation.

I don’t think item 5 exists In this country. The NIR class 80 DMUs which are now all withdrawn had a straight air brake with e.p. assist to speed up the application rate.
Old SR emus had an energise to apply e.p. Brake that was not fail safe. These had a brake pipe that was always charged to 70 psi and in even of train division or failure of the e.p. Brake venting this pipe initi and Emergency brake application. These systems are now only on heritage units.

For item (5) I was trying to describe what I believe the current UIC standard for "indirect" EP brakes. That is when the EP brake is applied (EP valves deliver air from MRP to brake cylinders) the pressure in the air brake pipe is reduced at the same time in order to give a fail-safe application. (As opposed to (older?) EP brakes in UK where the brake pipe remains at 70psi during normal EP brake applications and the ABP is only used if the EP brake fails.)

The system that you are describing for the NIR 80 class sounds like an SME or SMEE brake system. (Straight air, Motor and Emergency or Straight air, Motor and Emergency Electro-pneumatic.) These were widely used on subway trains in USA and on EMU trains in Japan. The air brake pipe (or Emergency pipe) remains charged at 70psi. The straight air pipe is at 0psi when the brakes are released and increased up to a maximum of 60psi during service braking.

Old SR emus had an energise to apply e.p. Brake that was not fail safe. These had a brake pipe that was always charged to 70 psi and in even of train division or failure of the e.p. Brake venting this pipe initi and Emergency brake application. These systems are now only on heritage units.

That is my item ( 4 ). This was the original "EP" brake introduced on the later standard stock on the London Underground and then later used on BR for all EMU units starting with the Southern 4-EPB units, and continuing through other dc and ac EMU units. On older units like the 4-EPB the driver had a brake controller that had separate EP and air positions (and as you say the air brakes only had conventional triple valves). On later units (CIG, VEP, REP and ac units) the driver had a switch to change from EP braking to air braking if the EP system failed (these later units had a distributor rather than a triple valve).

I had assumed that this system was still in use today on class 442, 455 and 456 as these were essentially derived from the same family. If that is not the case, then when did the change happen? Which were the last units to use the system where the brake pipe was always charged at 70psi during normal EP braking [Item (4)]? Which were the first units to reduce the air brake pipe pressure at the same time as applying the EP brake [Item (5)]?

The brake pipe on these vices is normally at atmosphere as it is only used for recovery. In the event that the unit requires to be hauled by a locomotive the brake pipe is charged to 5 bar and the brake system effectively becomes a two pipe air brake with the brake being released by the charged brake pipe without any ep electrical signal being needed.

Do any other trains have a similar system to allow for rescue (80x class?) or is this unique to those units?

Is the braking system on Pendolino trains the same as on Voyagers?

 

[DownFast]

455/456 have a simple energise to release EP brake, no brake pipe.

80x have a connector on an adaptor coupler for connecting a brake pipe connection from a loco for loco hauling, with a translator that converts brake pipe pressure into an EP brake signal, enabled by a 'loco-hauled mode' switch on the cab back wall. Again, no brake pipe.

 

[darwins]

Thanks very much.

So almost all questions answered. What remains concerns class 442, Pendolino... and the one I forgot to include Mk5 cars.

Class 442
The 4-REP units, as far as I know, used the older system where the brake pipe remained at 70psi and service braking was done with the EP brake only. Is this the same on class 442 or are is the air brake pipe pressure on these units reduced when the EP brake is applied?

Pendolino
Any information or answers to the above questions welcomed.

Mk 5 cars
I believe the regular trailer cars are standard air twin pipe with no provision for EP braking. What about the driving trailers - can they initiate braking from the both ends of the train as Mk3 and Mk4 DVTs can?

 

[Efini92]

All of todays multiple unit trains don't have a brake pipe at all. The compressed air line down the train merely feeds a compressed air supply to air reservoirs on each coach. Brake control is carried out entirely electrically, and sorts out when dynamic braking and when friction braking is used and when the former needs to be supplanted by the latter. The brake control doesn't have "steps" as such.

Some multiple units do have a brake pipe that is used for rescue. For normal operation it’s vented.

 

[darwins]

Some multiple units do have a brake pipe that is used for rescue. For normal operation it’s vented.

Voyagers and Meridians have been mentioned above in this category. Which other units (if any) have a brake pipe for rescue?

 

[Efini92]

Voyagers and Meridians have been mentioned above in this category. Which other units (if any) have a brake pipe for rescue?

Pendolinos.
The new CAF units have something when being assisted by loco but not sure if it’s a conventional brake pipe.

 

[GC class B1]

The CAF mk 5 TPE and sleeping cars have a two pipe UIC brake. The sleeping cars work with only a loco so are your type 2. I don’t know if the TPE units are your item 2 or 3.
To be accurate the SR energise to apply and the voyager/meridian systems cannot be operated as true two pipe air brake. In the SR energise to apply system with triple valves the Brake Supply reservoir is only charged from the brake pipe by the triple valve And not charged from the Main Res pipe.
The voyager does not have a distributor, the brake unit is controlled by the brake pipe instead of the electrical signal when loco hauled.

 

[sheepy1991]

Class 745 and 755’s fall into two categorys much the same as Pendolino, Voyager and the above mentioned CAF stock, whilst they use a CanBus / TCMS controlled EP brake (Category 6) they also have effectively a single pipe arrangement fitted for rescue purposes so any locomotive with the correct emergency coupler can pull them clear of the line.

Its a shame more classes of modern rolling stock do not have this feature as a standardised spec especially when fitted with the same manafacturers kit. Class 720’s use a Knorr-Bremse brake system as the 745 and 755 but do not have this feature.

In regards to the class 745 and 755 the rescue brake pipe is not a variable pipe (or so we have been told) so it does mean the towed 745 / 755 either has full brake release or the equivalent of an emergency brake being applied. Which it turn requires a a 50% reduction in line speed as decreed by the powers that be.
Its put into use by the operation of several “tow mode” cocks located in various areas of the units dependant on the Class.

 

[hexagon789]

In regards to the class 745 and 755 the rescue brake pipe is not a variable pipe (or so we have been told) so it does mean the towed 745 / 755 either has full brake release or the equivalent of an emergency brake being applied. Which it turn requires a a 50% reduction in line speed as decreed by the powers that be.
Its put into use by the operation of several “tow mode” cocks locat

Surely if it's a traditional single pipe without graduated release then an application can be graduated up to maximum but any release must be a full release.

Ie how the old SR slammer EMU/DEMUs operated on the auto air brake.

 

[TheEdge]

Its a shame more classes of modern rolling stock do not have this feature as a standardised spec especially when fitted with the same manafacturers kit. Class 720’s use a Knorr-Bremse brake system as the 745 and 755 but do not have this feature.

Its worth pointing out in a rare example of the railways seemingly doing something intelligent someone actually thought about this problem. 745s all carry in a box underneath them a 745/720 coupling adapter. The logic being if a 745 falls down catastrophically on the GEML (once the 321s go) either directly in front or behind will either be another 745 or a 720 so a rescue can be mounted regardless. And in the other way a 745 can rescue a 720.

 

[darwins]

So this seems to be the answer:

1. Single Pipe Air Brake - Freight trains

2. Twin Pipe Air Brake
- "loco" hauled passenger trains including Mk 5 carriages (and DVTs?)

3. Twin Pipe Air Brake (with provision for application from both ends of the train at the same time)
- HST, Class 90 or Class 91 with Mk 3 DVT or Mk 4 DVT

4. Indirect EP Brake (where air brake pipe remains at 70psi / 3.5bar during service application)
- class 442?

5. Indirect EP Brake (where air brake pipe pressure is reduced during service application)
- Not used in UK? (class 442?) (Eurostar?)

6. Direct EP Brake
no brake pipe for normal operation - fail safe provided by electrical continuity - "energise to release"
*have provision for rescue using standard air brake

( a ) 3 step brake - classes 150 to 168, classes 313 to 333, 455, 456, Networker, Electrostar

( b ) 7 step brake - Voyager*/Meridian*, Pendolino*

( c ) Pulse modulated brake - classes 170 to 185, class395, Juniper, Desiro, Aventra, Civity*, Flirt*, IEP*

7. SMEE direct brake ( straight air brake for service application )
- NIR class 80

Many thanks to all who have contributed so far. I am still very interested to learn anything about how rescue brakes work for the newer trains. I presume that operation of the Pendolinos along the North Wales Coast was using "rescue" brakes!

Where do Eurostar trains(either the old or new ones) come into this?

 

[GC class B1]

One more class to add. Class 230 ( and 484?) have a 3 step brake that was converted from the LUL 7 step direct e.p brake.

I would also suggest that class 442 had a direct ep brake ( not indirect) as it is energise to apply and is applied by electrical signals from the drivers brake controller.

The energise to release ep brake application is set by signal from the drivers brake controller being used by the BCU in each vehicle to set the correct brake cylinder pressure. In the case of the class 442 the control is by the drivers brake controller energising the apply relays on each vehicle until the desired brake cylinder pressure is registered on the vehicle with the active cab.

 

[sheepy1991]

Its worth pointing out in a rare example of the railways seemingly doing something intelligent someone actually thought about this problem. 745s all carry in a box underneath them a 745/720 coupling adapter. The logic being if a 745 falls down catastrophically on the GEML (once the 321s go) either directly in front or behind will either be another 745 or a 720 so a rescue can be mounted regardless. And in the other way a 745 can rescue a 720.

Unfortunately the emergency coupler you speak of which sits under Coach E is only mechanical, there is no brake compatibility between a 720 and 745. Even with the 745’s rescue brake pipe as a 720 cannot control a brake pipe like a Loco does, so it would be an unbraked move with severe speed restrictions. That emergency coupler being used will be an absolute last resort.

Its one of several reasons there is a push to remove the 745’s from the WA route. A 720 /745 rescue is far from ideal and its not so easy for a loco rescue on the WA as it is on the GE.

 

[Poppysdad]

Almost all multiple units operating in the UK since Class 313's onwards have utilised an EP controlled brake without a brake pipe, initially with a 3 step brake using digital train wires operating a grey code sequence.

With the post privatisation fleets Alstom changed the train wire demand on fleets such as Juniper and Coradia to use PWM. Bombardier with the Electrostar platform continued to use digital brake demands on the Electrostar and Turbostar platforms.

The trainline demand then changed again to use the Trainbus for the brake demand such as MVB.

The blending of the friction brakes with the dynamic brakes (Electric or Hydro dynamic) generally works the same irrespective of the trainlined demand and have also evolved .

1. Older trains only blended within the motor car, either programmed blend or continuously blended
2. Trains then blended between cars such as motor and trailer pairs
3. Modern trains now blend within the brake network

 

[Irascible]

Surely if it's a traditional single pipe without graduated release then an application can be graduated up to maximum but any release must be a full release.

Ie how the old SR slammer EMU/DEMUs operated on the auto air brake.

If you're going to put a triple valve in you might as well put a distributor in. This doesn't sound like either though, very wierd - anyone got the name of the brake system?

 

[hexagon789]

If you're going to put a triple valve in you might as well put a distributor in. This doesn't sound like either though, very wierd - anyone got the name of the brake system?

That is a good point, but the behaviour described sounded more in keeping with a triple valve system even if it isn't necessarily such.

 

[GB]

There are some freight trains that operate as twin pipe brake. Network Rail's High Output Ballast Cleaner and Track Renewal System being examples. Some aggregate wagons too.

 

[GC class B1]

There are some freight trains that operate as twin pipe brake. Network Rail's High Output Ballast Cleaner and Track Renewal System being examples. Some aggregate wagons too.

Yes, I believe this is to provide an air supply to operate equipment on the wagons.